The Newtown, Conn., shooter was motivated by violent video games and set out to kill more people than another mass murderer, CBS News reported Monday, citing law enforcement sources.

Adam Lanza -- who killed 26 people, including 20 children, at Sandy Hook Elementary School in December -- reportedly wanted to surpass the 77 killings by Norwegian Anders Breivik in 2011. Breivik killed eight people in a bombing in Oslo and fatally shot another 69 people, mostly teenagers at a summer camp, on a nearby island. CBS News reported that police found evidence of Lanza's obsession with Breivik.

CBS News also quoted sources saying Lanza chose the school because it was the "easiest target" with the "largest cluster of people." They also reportedly have evidence showing that he was acting out video game fantasies with the deaths equaling some sort of "score." He reportedly spent hours alone in his basement playing video games and practiced shooting real guns with his mom at a shooting range.

Connecticut State Police Lt. J. Paul Vance told CBS News that the investigation is ongoing and that any comment on motive is speculation.

Lanza killed himself as police closed in the morning of the Dec. 14 tragedy in Newtown. The massacre reignited a debate about violence in Hollywood product, including movies, TV shows and video games.

A poll conducted by The Hollywood Reporter and Penn Schoen Berland in early January found that 70 percent of respondents over age 30 believe there is too much violence depicted in advertising for movies and TV, while 46 percent of respondents said Hollywood should make fewer movies that feature violence and killing.